Robert Horst Verified User

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  • Robert Horst

    Post
    (Quote from THHuxleynew)

    Yes, you are right that the equation works for a 3 ohm sense resistor. It is easier to see this way:

    If A is the voltage across a 3 ohm resistor, then I=A/3 or A=3I. Substituting, into:
    P= (V*A)*0.3333-(A*A)/3
    you get
    P = VI -3I2
    and…
  • Robert Horst

    Post
    (Quote from Paradigmnoia)

    It looks like he is measuring blower power as the total power from the supply minus the power lost in the current sense resistor.

    Resistor power is I2R, and the (A*A)/3 corresponds to the power through a 1/3 ohm (.3333 ohm)…
  • Robert Horst

    Like (Post)
    Thanks to Bob Greenyer of MFMP for making another excellent recording of Mitch Swartz' presentation at at ICCF-22

    youtube.com/watch?v=D6kJsEWyJ8g&feature=youtu.be
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    (Quote from Ascoli65)

    You may be right the the cause is related to the turbulent air, but realize that the data points in the spreadsheet are 25 seconds apart. It is hard to imagine a vortex that lasts 25 seconds or longer and makes the average 2 deg C…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    No, I do not think plasma heating or any other heater-related noise could lead to the output temperature variations. If you look at my first graph above (just edited to fix the horizontal scale), the large output temperature variations last for more…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    On a slightly different subject, I have been wondering why there is large variation in the output temperatures while the heater is on, but not when it is off. Here is a graph I produced from the Mizono spreadsheet:

    The temperature varies +- 2 degC…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    Experiments that use an internal heater have a different equivalent thermal circuit than the one I posted earlier. This circuit would apply to R20 as well as the earlier experiments if they also use an internal plasma heater.
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    (Quote from THHuxleynew)

    It is hard to draw many conclusions based on the long time constant at the tail of the experiment. The amplitude of the tail is less that 1 degree which is much less than the errors in the rising edge measurements. That means…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    (Quote from RobertBryant)

    1. Does the SPICE sim give a regression value saying how good the fit is on the heating phase , and on the cooling phase?


    No. SPICE does not do that directly. There are ways of varying parameters or adding comparisons to…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    There is more than one time constant in the Mizono experiment and the interactions between them are not easily solved without simulation tools. The same differential equations for heat flow are the ones used in EE for RC circuits. I have created a…
  • Robert Horst

    Like (Post)
    Just wanted to give much thanks to rubycarat for her on the fly coverage, the next best thing to being there for all of us who had no possibility of being there.

    You are doing a great work Ruby!!!
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    I think you are using "input" to mean different things. Jed says Mizono measures input to the heater and you are talking about input to the power supply powering the heater. Your posts would be clearer if you used "heater input" or "power supply…
  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    Restricting the flow does not increase the volume of air. It decreases the volume from the blower less than it decreases the flow from the axial fan. You can see this when you look at pressure/velocity curves like this.

  • Robert Horst

    Replied to the thread Mizuno Airflow Calorimetry.
    Post
    (Quote from Paradigmnoia)

    Blowers generally deliver air at higher pressure but lower velocity than axial fans.

    When testing, if you restrict the output flow to increase backpressure, there will be some point where the blower delivers more air (CFM) than…
  • Just as with the other Mizono-type experiments, much could be learned in the Zhang experiment from showing graphs while cycling the input power on and off at some interval longer than the thermal time constant.
    • Is the output delay for excess heat the